The present invention relates to an exterior sideview mirror assembly suitable for mounting on a vehicle and, more particularly, to an exterior sideview mirror assembly which incorporates a skullcap or shell or scalp to provide a decorative appearance to the assembly.
Conventionally, vehicles are equipped with at least a driver's side exterior mirror assembly, which is mounted either to the body of the vehicle or in the door frame of the vehicle. More often, vehicles are also equipped with a passenger side exterior mirror assembly which is typically mounted to the opposite side of the vehicle in a similar fashion to the driver's side exterior mirror assembly. The trend in exterior rearview mirror assemblies has been to form an exterior mirror assembly which exhibits better aerodynamic characteristics and, further, which has an aesthetic appearance, preferably with the exterior mirror assembly being decorated to have a high gloss and/or to match the vehicle body paint.
However, more recently in an attempt to reduce the cost of manufacturing such assemblies, a composite assembly has been developed which includes a frame and a shell or skullcap or scalp, which is mounted to the frame, for example by snap connectors. The frame is formed from an engineering plastic, typically a reinforced engineering plastic, such as reinforced nylon or the like. The shell or skullcap is also formed from a plastic substrate which is then painted to match the vehicle body color. The structural capacity of the housing is provided by the frame, with the shell providing a decorative covering over the frame so that the housing generally matches the vehicle body. As a result, however, the wind noise of the side exterior mirror assembly can be increased. This wind noise is generated such as by the space between the decorative shell and the frame of the mirror assembly.
Various attempts have been made to minimize and/or eliminate the wind noise. One approach is to eliminate the space between the decorative shell and the frame. However, in order to eliminate the space, the tolerances on the respective parts must be extremely tight, which adds the expense of the sideview exterior mirror assembly fabrication. Another approach is to alter the surface topology of the decorative shell to separate the air flow over the side exterior mirror assembly, which reduces the noise of the wind flow. For example, in German Patent 4,039,484 to Bayerische Motoren Werke AG, a plurality of raised portions or “bumps” are provided to separate the air flow over the housing. However, these raised portions are not aesthetically pleasing to some automobile manufacturers and, further, project above the assembly and create a distraction to the driver. In addition, it has been found that when a discontinuity is introduced into the substrate of the skullcap (such as when it is molded in a molding tool), that the noise reduction advantages of such a surface molded discontinuity is reduced drastically by the painting process which follows since the painting process alters the surface topology of the substrate and, rather than following the surface discontinuities, at least partially fills in the discontinuities.
Consequently, there is a need for an exterior rearview mirror assembly which incorporates a decorative skullcap that exhibits reduced noise while retaining the aesthetic appearance of the mirror assembly.